Define function to create a 'diagonal' array or get the diagonal of an array

Usage

diag3Darray(x = 1, dim = length(x), out = "vector")

Arguments

x: number or vector defining the value of the diagonal of 3D array
dim: integer defining the length of the diagonal. Default is length(x). If length(x) != 1, dim must be equal to length(x).
out: character specifying which type of diagonal to return ("vector" or "matrix"). See Details

Value

array with all elements zero except the diagonal, with dimensions c(dim,dim,dim)

Details

The diagonal of a 3D array has been defined as those elements in positions c(int,int,int), i.e., the three digits are the same.

If the diagonal should be returned, out specifies if it should return a "vector" with the elements of position c(int,int,int), or "matrix" with the elements of position c(int,dim,int), i.e., dim = 2 -> elements (1,1,1),(2,1,2),(3,1,3),(1,2,1),(2,2,2),(3,2,3),(3,1,3),(3,2,3),(3,3,3).

Examples

x <- diag3Darray(c(1,4,6), dim = 3)
x
#> , , 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    0    0
#> [2,]    0    0    0
#> [3,]    0    0    0
#> 
#> , , 2
#> 
#>      [,1] [,2] [,3]
#> [1,]    0    0    0
#> [2,]    0    4    0
#> [3,]    0    0    0
#> 
#> , , 3
#> 
#>      [,1] [,2] [,3]
#> [1,]    0    0    0
#> [2,]    0    0    0
#> [3,]    0    0    6
#> 
# , , 1
#
# [,1] [,2] [,3]
# [1,]    1    0    0
# [2,]    0    0    0
# [3,]    0    0    0
#
# , , 2
#
# [,1] [,2] [,3]
# [1,]    0    0    0
# [2,]    0    4    0
# [3,]    0    0    0
#
# , , 3
#
# [,1] [,2] [,3]
# [1,]    0    0    0
# [2,]    0    0    0
# [3,]    0    0    6
diag3Darray(x)
#> [1] 1 4 6
# 1, 4, 6